During the production of semiconductor dice or chips, many semiconductor dice are formed together on a single wafer. The wafer is then cut to separate the individual dice. Each of these semiconductor dice should then be individually mounted onto a support surface for further processing by utilizing a die bonding process. Thereafter, electrical connections are created between the dice and external devices, and the dice are later encapsulated with a plastic compound to protect them from the environment.
In prior art die bonders the die bonding process includes the step of picking up an individual die with a bond arm from the wafer. The die is then transported to a bonding site for bonding onto a substrate which has an adhesive dispensed thereon to attach the die onto the substrate. A single head dispensing system is usually deployed to dispense an adhesive material onto the substrate. In order to increase throughput of the operation dispensing systems with dual heads may be used.
FIG. 1 is a front view of a conventional die bonder 100 incorporating a dual-head dispensing system for dispensing adhesive such as epoxy. The dual-head dispensing system comprises first and second epoxy dispensing heads 102, 104 mounted on separate XYZ motion tables. The first and second dispensing heads 102, 104 are equipped with an optical system each for pattern recognition of a position of a substrate before epoxy dispensation. The two dispensing heads 102, 104 are spaced apart and are movable independently on two separate work stations or conveyor mechanisms for dispensing adhesive from first and second dispensing nozzles 105, 107. Each work station comprises a set of vacuum holes 106 which may be arranged in a column for providing vacuum suction to hold a substrate firmly on an anvil block. FIG. 2 is a top view of an anvil block 108 with two columns of vacuum holes 106 aligned adjacent to each other.
FIG. 3 illustrates a top view of a substrate or leadframe 110 that is held on the anvil block 108 of FIG. 2 by vacuum suction provided through the vacuum holes 106 on the anvil block 108. The positions of the first and second dispensing heads 102, 104 correspond to the arrangements of the two columns of vacuum holes 106. The two columns of vacuum holes 106 are in turn separated by a gap 112 determined by a column pitch 114 which separates two columns of die pads 116 on the leadframe 110. Typically, the column pitch 114 ranges from 2 mm to 70 mm. The smallest gap 112 achievable is limited by the geometrical arrangement of the first and second dispensing heads 102, 104.
As such, the arrangement of the first and second dispensing heads 102, 104 is constrained by the configuration of the leadframe 110. To cater for a complete range of column pitches 114 and to accommodate the sizes of different leadframes 110, a dispensing table with a long travel trajectory in the X-direction and a long anvil block 108 are required. Therefore, the space needed to accommodate multiple dispensing heads and the associated work stations is large and would be a serious limitation when there are space constraints. Furthermore, it is difficult to ensure that a long anvil block 108 is maintained totally flat in order to avoid vacuum leakage. As such, designs without screws are not possible due to the fear of vacuum leakage. It is therefore desirable to provide a dual-head dispensing system which is able to take up a smaller footprint as compared to the prior art described above.